🚀 Create aarch64 MUSL version

Hello there,

I love using delta and on my mac a popular choice for many projects is alpine linux. This uses musl vs. glibc and on my mac is aarch64 by default.

Any issues with adding that to the list of released files, I was thinking a ```delta-0.18.2-aarch64-unknown-linux-musl.tar.gz``` would be sufficient and work the same as with debian. Let me know any concerns, I'll see if this is something I can send a pull request for,